Living off the grid

I read something on Digg the other day about how more and more Americans are living off the grid or at least trying to. Unfortunately, they're doing it for the wrong reason. Decentralizing power and food generation should be done in the name of efficiency. High voltage power lines are pretty efficient, but even a one percent loss during transmission adds up quickly over time so it makes sense to generate all necessary power on-site.

Most of the people quoted in the article are concerned about what happens when American society collapses and hungry folk try to storm their compound. Somehow living off grid now involves hoarding food and stocking up on weapons. Uh...yeah. One old codger said his car and house were configured to run off natural gas. Natural gas eh? The same stuff that also needs to be pumped out of the ground? The same stuff that is also finite? Oh, that's much better than gasoline or heating oil. Yikes.

The most reliable alternative energy source right now is solar. While efficiencies are still below fifty percent, more and more companies are investing in developing panels and arrays because they can smell the future. Most of the recruiters here in Silicon Valley spamming my e-mail and voice mail are looking for people to help develop solar. My cousin just got a job in Phoenix helping to sell solar systems. Why not? The sun shines more than three hundred days per year there so you might as well take advantage of it. If everyone could put three or four panels on their roofs, we could probably reduce the number of power plants necessary. It would certainly reduce the number of brownouts and we could reduce the number of high voltage lines running around so that we can minimize our impact on this planet.

Since I'm a big dork, I was trying to figure out if solar panels could help insulate your home. The sun's output is pretty broadband (shown in the picture horked from the web) and is much broader than Si's absorption spectrum (Si is the main element in a solar cell). Let's say half of the sun's output can be absorbed by Si (the cutoff is 1100 nm which seems to be more than half on the graph, but we want to account for reflection as well). However, solar cell efficiencies are around forty percent so a solar cell could only convert about twenty percent of incoming light to electricity. The rest is either reflects or generates heat.

Wind power is becoming more and more popular, but large towers are needed to extract sufficient energy and most people don't have the land to put up 200 foot tall towers. I've seen websites selling smaller cylinder systems, but their efficacy has not yet been proven.